The EndPoint cannot be null

	The EndPoint argument in Begin/EndSendTo cannot be null.

mcs/class/System/System.Net.Sockets/Socket.cs

@@ -908,6 +908,9 @@ namespace System.Net.Sockets
 			if (buffer == null)
 				throw new ArgumentNullException ("buffer");
 
+			if (remote_end == null)
+				throw new ArgumentNullException ("remote_end");
+
 			if (offset < 0)
 				throw new ArgumentOutOfRangeException ("offset", "offset must be >= 0");
 

mcs/class/System/System.Net.Sockets/Socket_2_1.cs

@@ -1765,6 +1765,9 @@ namespace System.Net.Sockets {
 			if (result == null)
 				throw new ArgumentNullException ("result");
 
+			if (end_point == null)
+				throw new ArgumentNullException ("remote_end");
+
 			SocketAsyncResult req = result as SocketAsyncResult;
 			if (req == null)
 				throw new ArgumentException ("Invalid IAsyncResult", "result");